Was it? In 1542, I know that Spanish America banned slavery of indigenous Americans. In Russia, slaves could be Russian or any race, no racial curbs at all. Back when China was divided and warring each other, slaves were mostly Chinese. And the old three Vietnamese kingdoms enslaved each other, too.

I have read several pages of the first issue of Dabiq. One thing I have noticed is that ISIS is really good at propaganda. The quality of the magazine is pretty high. It tries to portray itself as a utopia while they are actually a dystopia in reality.